Checking for selecting

[Suji]

Hi there !

I'm new in the programing world. I'm trying to do a simple QActionGroup which allows me to check for selecting between multiple availables cameras. I'm creating the QActiongroup menu like this (thanks QT examples) :

 camerasMenu = menuBar()->addMenu(tr("&Cameras"));

    QActionGroup *groupeCameras = new QActionGroup(this);
    groupeCameras->setExclusive(true);
    foreach (const QCameraInfo &cameraInfo, QCameraInfo::availableCameras())
    {
        QAction *groupeCamerasAction = new QAction(cameraInfo.description(), groupeCameras);
        groupeCamerasAction->setCheckable(true);
        groupeCamerasAction->setData(QVariant::fromValue(cameraInfo));
        if (cameraInfo == QCameraInfo::defaultCamera())
            groupeCamerasAction->setChecked(true);

        camerasMenu->addAction(groupeCamerasAction);

            qDebug() << cameraInfo.description();
    }

Actually, i setup the viewfinder like this, manualy :

    QCameraViewfinder *viewfinder = new QCameraViewfinder(this);
    setCentralWidget(viewfinder);

//Display Video stream

    foreach (const QCameraInfo &cameraInfo, cameras)
        {
            qDebug() << cameraInfo.description();

            if (cameraInfo.description() == "cameraname")
                camera = new QCamera(cameraInfo);
        }
    camera->setViewfinder(viewfinder);

Then i just connect "camera" to a simple pushbutton "on" that activate the stream.

I want to be able to change the default camera by checking the camera desired on this QActiongroup, then when i click on my "on" button, that start the stream of the camera checked, and not the camera that i'm actually manualy choose.

Am I clear ? :s

Have a good day !

Suji

[raven-worx]

@Suji

the line QVariant::fromValue(cameraInfo) only works if the type is already registered as a meta type to Qt. I am not sure if QCameraInfo is registered as such (you will receive an error if not).

If not you need to add it (somewhere before using it):

Q_DECLARE_METATYPE(QCameraInfo) // put this in a header file
qRegisterMetaType<QCameraInfo>(); // maybe in the constrcutor, or a static initializer

Or simply add the description string to avoid this at all.

Either way connect to the QActionGroup triggered(QAction)* signal in case you want to immediately react on the changes or use QActionGroup::checkedAction() to get the currently selected action.
From the action then retrieve the data you already set using QAction::setData().

[kshegunov]

@raven-worx
Actually,

Q_DECLARE_METATYPE(QCameraInfo)

is enough for QVariant, qRegisterMetaType<QCameraInfo>() one needs for queued connections.

[raven-worx]

@kshegunov
yes right.
It's a personal habit of mine to also call qRegisterMetaType() along with Q_DECLARE_METATYPE

[Suji]

hi ! Thanks for your answers!

I've already fixed the meta type problem by the past by adding Q_DECLARE_METATYPE(QCameraInfo) in the .cpp file, seems to work like this, but is it better to put it into the header even if Qt dont send any error ?

I started to use the QActionGroup triggered(QAction)* signal like this :

QAction *checkedButton = groupeCameras->checkedAction();
groupeCameras->triggered(checkedButton);

(As reminder : groupeCameras is the QActionGroup.)

I dont know how to do after this. I'm thinking about setting the checked camera as "defaultcamera" and construt the QCamera on it like this for example :

QCameraInfo camdefault = QCameraInfo::defaultCamera();
camera = new QCamera(camdefault);

But i dont know how to link QAction to a QCamera in fact...

Thanks a lot again for your help !

[raven-worx]

@Suji
the triggered() is a signal not a method you should call.

connect( actionGroup, SIGNAL(triggered(QAction*)), this, SLOT(onActionSelected(QAction*)) );
....

// must to be declared as slot
void onActionSelected(QAction* action)
{
       QCameraInfo info = action->data().value<QCameraInfo>();
       ....
}

Checks left out for this example.

Or if it's easier for your code design use

QAction* action = actionGroup->checkedAction();
QCameraInfo info = action->data().value<QCameraInfo>();

at a appropriate place.

[Suji]

Thank you,

Yes, my coding method is not clean, i'm learning alone, so it's harder to have clean habits. I will use your first example, it's seems to be a good way for resolving my problem + learning how to code properly.

Now i'll try to go ahead alone, i hope it will be good !

Thanks again @raven-worx, wish you a good day !

[Suji]

Hi again,

Your solution worked well, now when i check on the QActionGroup groupeCameras, that selects the camera as i wanted.
But now, i want to display the camera's stream i choosed, but i got this answer back in the command window :

• "CamChoosed"
  Failed to get the video control

Did i miss something obvious ?

Here is the code :

connect(groupeCameras, SIGNAL(triggered(QAction*)), this, SLOT(onActionSelected(QAction*)) );

void MaFenetre::onActionSelected(QAction* action)
{
       QCameraInfo info = action->data().value<QCameraInfo>();

               qDebug() << info.description();
                camera = new QCamera(info);
                camera->setViewfinder(viewfinder);
                camera->start();
}

[SGaist]

Hi and welcome to devnet,

You don't seem to delete the original camera before creating a new one thus I'm not sure that you can change your viewfinder like that.

[Suji]

Hi @SGaist !

I moved the 2 lines :

QCameraViewfinder *viewfinder = new QCameraViewfinder(this);
 setCentralWidget(viewfinder);

from my principale function to the MaFenetre::onActionSelected function, and that work !

Thanks a lot guys, you're magic here ! I was searching for days !